There's also a video to help, which I've added below.
Hope this inspires you to build something of your own for the kids.
Welcome to the Bunnings Workshop community @AH. It's brilliant to have you join us, and many thanks for your question about this amazing project.
Taking a look at the plans and making an educated guess, I'd say the ship is in the vicinity of 2400mm long and 1300mm wide. According to the plans, it's definitely 1300mm wide, and those straight sides are 1800mm long. You then have the bow, made from 800mm long sleepers, angled into a point that would reduce their length.
Are you planning on constructing this sandpit? If so, I trust our members would love to follow along. Please let us know if you need any assistance or have further questions.